Magpul makes a ton of wonderful products for the AR platform. This is not one of them. As stated this product is compatible with both Milspec and Commercial buffer tubes, that's what makes this GARBAGE. Installation of this product makes you want to beat your head against a wall. I've assembled over 100 lowers to date, using this product in about 5 of those builds (not my choice). Installation of this product is a tedious, tedious endeavor once you select the correct locking pin for the buffer tube. Save yourself some serious time, frustration, money, and purchase the DSG Ambi Loop.